Surface Conditioning of 316LVM Slotted Tube Cardiovascular Stents

Raval, Ankur; Choubey, Animesh; Kothwala, Devesh

doi:10.1177/0885328205046564

Cited by 20 publications

(20 citation statements)

References 7 publications

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“…In addition, the corrosion resistance of stent alloys is critically dependant on their formation of a protective oxide film. [26][27][28] Surface treatments such as electropolishing and passivation create oxides with thicknesses in the range of 50-100 Å 29 and which are relatively uniform with limited surface defects. Mechanical damage as a result of rubbing against calcification could lead to removal of this oxide layer and if the rate of repassivation is slowed as a result of decreased aeration in the invivo environment, a potential for corrosion arises.…”

Section: 2mentioning

confidence: 99%

The role of vascular calcification in inducing fatigue and fracture of coronary stents

Halwani¹,

Anderson²,

Brott³

et al. 2011

J Biomed Mater Res

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Traditional approaches for in-vitro pulsatile and fatigue testing of endovascular stents do not take into consideration the pathologies of the stented vessel and their associated biomechanical effects. One important pathology is calcification, which may be capable of inducing changes in the vessel wall leading to inhomogeneous distribution of stresses combined with wall motion during the cardiac cycle. These local property changes in the region adjacent to stents could directly influence in-vivo stent performance. Seven cases containing a total of 18 stents were obtained from autopsy. Radiographs were evaluated and vessels were sectioned for histology and stent topographical analysis. Stents were retrieved by chemical removal of surrounding tissue and surfaces were evaluated using 3D digital optical and scanning electron microscopy for biomechanical abrasion and fracture features. Pathologic complications such as restenosis and thrombus formation were assessed from histological sections. Direct evidence of fracture was found in 6 of the 7 cases (in 12 out of 18 stents; 9 drug eluting and 3 bare metal). The degree of stent alterations was variable, where separation of segments due to fracture occurred mostly in drug-eluting stents. All fracture surfaces were representative of a high cycle fatigue mechanism. These fractures occurred in complex lesions involving the presence of diffuse calcification alone, or in combination with vessel angulations and multiple overlapping stents. Morphologic analysis of tissue at or near some fracture sites showed evidence of thrombus formation and/or neointimal tissue growth.

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Section: 2mentioning

confidence: 99%

The role of vascular calcification in inducing fatigue and fracture of coronary stents

Halwani¹,

Anderson²,

Brott³

et al. 2011

J Biomed Mater Res

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“…However, it is generally assumed to involve two discrete reactions at the anode surface that are termed anodic leveling and brightening [22][23][24]. The dissolution rate at valleys and peaks during the electropolishing is dependent on the current distribution or on the mass transport conditions, leading to an anodic leveling of the surface.…”

Section: Introductionmentioning

confidence: 99%

Electropolishing of medical-grade stainless steel in preparation for surface nano-texturing

Nazneen

Galvin

Arrigan

et al. 2011

J Solid State Electrochem

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The purpose of this work is to investigate the electropolishing of medical-grade 316 L stainless steel to obtain a clean, smooth, and defect-free surface in preparation for surface nano-texturing. Electropolishing of steel was conducted under stationary conditions in four electrolyte mixtures: (A) 4.5 M H 2 SO 4 + 11 M H 3 PO 4 , (B) 7.2 M H 2 SO 4 + 6.5 M H 3 PO 4 , (C) 6.4 M glycerol + 6.1 M H 3 PO 4 , and (D) 6.1 M H 3 PO 4 . The influence of electrolyte composition and concentration, temperature, and electropolishing time, in conjunction with linear sweep voltammetry and chronoamperometry, on the stainless steel surface was studied. The resulting surfaces of unpolished and optimally polished stainless steel were characterized in terms of contamination, defects, topography, roughness, hydrophilicity, and chemical composition by optical and atomic force microscopies, contact angle goniometry, and X-ray photoelectron spectroscopy. It was found that the optimally polished surfaces were obtained with the following parameters: electrolyte mixture A at 2.1 V of applied potential at 80°C for 10 min. This corresponded to the diffusion-limited dissolution of the surface. The root mean square surface roughness of the electropolished surface achieved was 0.4 nm over 2×2 μm 2 . Surface analysis showed that electropolishing led to ultraclean surfaces with reduced roughness and contamination thickness and with Cr, P, S, Mo, Ni, and O enrichment compared to untreated surfaces.

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“…Additionally, cobalt-chromium stents are nontranslucent to certain electromagnetic radiation waves, such as x rays, and, relative to stainless steel stents, provide a higher degree of radiopacity, thus being easier to identify in the body under fluoroscopy. Detailed studies of micromachining of 316LVM stainless steel tubes using periodic acousto-optic modulation of pulsed Nd:YAG lasers for cardiovascular stent and characterization of laser beam parameters for optical microfabrication of ultra-hard and wide band-gap photonic materials for micro-optoelectromechanical systems ͑MOEMS͒ applications have been reported by Sudheer et al [23][24][25] Niziev et al reported the three-dimensional ͑3-D͒ theory of laser cutting and the cutting efficiency, which is determined by its ultimate parameters at different types of polarizations, is estimated. 26 The physical reasons for limitations of ultimate cutting parameters at a plane P-polarized beam are displayed.…”

Section: Acousto-optical Modulation Of Pulsed Nd: Yagmentioning

confidence: 99%

“…The slag in the laser-cut zone was not removed totally in the case of pickling with the HNO3+ electrolysis process; also the oxides produced by the lasercutting process still adhered to the surface of the stent. 25 Immersion time ͑5 h͒ could not be exceeded with this solution to avoid excessive stock removal, Whereas, after pickling for a short period of 15 min with HF + HNO3, the slag could be effectively removed from the laser-cut zone. Therefore, it can be considered that pickling with HF + HNO3 is more suitable for 316LVM and Co-Cr slotted tube coronary stents.…”

Section: Perchloric Acid 20%mentioning

confidence: 99%

Laser microfabrication of L605 cobalt-chromium cardiovascular stent implants with modulated pulsed Nd:YAG laser

Sudheer

Kothwala

Prathibha

et al. 2008

J. Micro/Nanolith. MEMS MOEMS

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Photonics modulation techniques can be effectively used for the laser microfabrication of biomedical implants to achieve better flexibility and control of the available optical power. These enable the processing and manufacturing of biomedical implants like cardiovascular stents and micro-metallic components with reduced heat affected zone ͑HAZ͒ and extremely precise edge cutting. Our investigation deals with the study of acousto-optic modulation of a pulsed Nd:YAG laser beam and further profile cutting of thin cobalt-chromium tubes for cardiovascular stent manufacturing. The acousto-optic modulator used in the investigations is a Bragg diffraction device. During one piercing process, the focused laser power is gradually varied from a low value and reaches the maximum as the beam goes deeper into the material. The optimum value for dwell time during which the laser piercing is occurring is found as 58 ms. A 14-step staircase modulating voltage with a maximum AC component of 900 mV was used, and the laser power was 4.4 W in TEM 00 operation. Pulsed Nd:YAG laser modulated using an acoustooptic device in the Bragg regime is capable of cutting extremely complex geometries of stents on L605 tubing. Laser cutting resulted in a kerf width of 22.5± 0.5 m. Precise strut dimensions of 112± 15 m for the subsidiary strut, 140± 15 m for the main strut, and 140± 15 m for the link were also obtained. Scanning electron microscopy ͑SEM͒ images of L605 stents illustrate the higher strength Co-Cr alloy L605 with the same ductility, its ability to be translated into thinner struts, and improved deliverability. L605 also exhibits enhanced radio visibility thanks to its tungsten content and exceptional work hardening rate for a uniform expansion with minimal recoil.

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Surface Conditioning of 316LVM Slotted Tube Cardiovascular Stents

Cited by 20 publications

References 7 publications

The role of vascular calcification in inducing fatigue and fracture of coronary stents

The role of vascular calcification in inducing fatigue and fracture of coronary stents

Electropolishing of medical-grade stainless steel in preparation for surface nano-texturing

Laser microfabrication of L605 cobalt-chromium cardiovascular stent implants with modulated pulsed Nd:YAG laser

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